Sivasrinivasu Devadula

Kerf profile generated by abrasive waterjet (AWJ) machining process has always been an interesting area as it dictates the quality of the part. However, due to the non-deterministic nature of the process, it is a challenging task to predict it. On the other hand, understanding and controlling the kerf profile in multi-layered structures (MLSs) is a further difficult task as various layers made of different materials respond to erosion in a different manner and results in a completely different kerf shape (barrel or x-shaped kerf profile) due to the material removal mechanisms dependency on the material property of the specific layers, jet divergence and position of specific layer. Therefore, it is important to understand and develop predictive models of resulting kerf profile in MLSs so that they can be used in controlling the accuracy of the resulting kerf which in turn dictates the final part accuracy. The attempts in this direction are very limited although some modeling efforts are reported in homogeneous materials (metals, ceramics). For the first time, an analytical model for predicting the kerf profile generated in MLS machining with AWJ was presented in this research work. Discretized form of Hashish model was used for determining depth of cut. The effect of jet divergence from the experimentally obtained values, upon passing through the upper layer has been considered. The developed predictive model was validated by the kerf shapes obtained from the experimental trials on metal-adhesive-rubber MLS. Kerf profiles obtained from the simulations have captured the resulted convergent-divergent (X-shaped) profile, while cutting metal-rubber laminate composite, effectively. Furthermore, the effectiveness of the proposed analytical model was demonstrated by generating the various kerf shapes generated at various jet traverse rates.

The CMS experiment will change it’s silicon tracker completely during phase-II upgrade. There is need to develop light and high precision and durable mechanical structure for silicon modules. The prime purpose of this should also be reducing material in the silicon tracker detector. The group at IIT Madras is involved in R&D of production of this structures. We have produced high precision bridge made of AL-CF material and carbon fiber stiffener.

The CMS experiment will change its silicon tracker completely during phase-II upgrade. There is need to develop light and high precision and durable mechanical structure for silicon modules. The prime purpose of this should also be reducing material in the silicon tracker detector. The group at IIT Madras is involved in R&D of production of this structures. The prime purpose of this should also be reducing material in the silicon tracker detector. We have produced high precision Al-CF bridges, stumps and Pipe connector 47 degrees for HgCAL detector.

Abrasive waterjet (AWJ) is an effective tool for manufacturing parts from multi-layered structures (MLSs) due to its capability in machining a wide range of materials. However, the challenge in employing AWJ in producing the desired kerf geometry in MLS can be attributed to the complex nature of the jet's interaction with multiple layers that possess different material properties. Hence, a model that captures the interaction of the jet with MLS, and predicts the whole kerf geometry is required to gain control over the kerf quality. On the other hand, the kerf generated in a layer is affected by the presence of preceding-/following- layers. In this context, it is essential to develop a comprehensive model for the prediction of kerf profile during the penetration of the jet in each layer. Although, several models exist to predict the process response (erosion depth, top (wt), and bottom kerf width (wb), kerf taper), very limited models available on kerf profile prediction. Further, neglecting the actual jet characteristics limits their ability to predict accurately. By considering the above, this work proposes a model for the prediction of the kerf geometry (profile and characteristics) in a single layer of MLS along with its kerf characteristics apart from considering the non-linearities, such as jet characteristics and the effects of AWJ process parameters. A discretized form of the jet, abrasives mass flow distribution, and their velocity in the jet plume to realize a more realistic model for predicting kerf geometry. Further, a new parameter, 'depth of damaged region’ was defined towards realizing the wt. The model was evaluated by comparing the kerf geometry formed on mild steel (MS) and aluminum (Al) materials by using root mean square and mean absolute error. The proposed model was found to predict the kerf geometry accurately.